Thermostatic switch



Aug. 14, 1928. 1,680,426

H. D. MATTHEWS THERMOS TAT I C SWITCH Filed April 23, 1926 WITNESSES: INVENTOR 3 @ww fiawardQNaff/vews I B WM 1 Y ATTORNEY Patented Aug. 14, 19 28.

UNITED STATES HO'WARD D. MATTHEWS, OF MANSFIELD,

OHIO, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

THERMOSTATIC SWITCH.

Application filed April 23, 1926. Serial No. 104,073.

My invention relates to temperature controlled devices, and particularly to thermostatic switches.

An object of my invention is to provlde a thermally-actuable switch assembly compr sing relatively few parts that may be eas1ly and quickly assembled and ad usted, and embodying contact bridgmg members dlrectly mounted on a thermally-actuable member.

Another object of my invention is to provide a thermally-actuable switch assembly that shall have opposed predetermined limiting positions to and from which it shall be actuated with a snap action.

In practicing my invention, I prov1de a supporting means, a bimetallic d1sc loosely mounted thereon, and a plurality of relatively fixed contact members, located at each side of the disc and adjustable relatively thereto longitudinally of the supporting means.

In the single sheet Fig. 1 is a view, portions in section, my invention,

Fig 2 is a view in lateral section therethrough taken on the line IIII of Fig. 1,

Fig. 3 is a view in lateral section therethrough taken. on the line III-III of Fi 1 Fig.1 is a view in lateral section taken on the line IV--IV of Fig. 1,

Fig. 5 is a fragmentary sectlonal view taken on the line V-V of Fig. 4, and

Fig. 6 is a fragmentary sectional vlew taken on the line VIVI of Fig. 4.

A thermally actuable switch 11 com rises a central stud 12 having portions of di erent external diameter, each of which is provided with screw-threads, base members 13 and 14, and a thermally-actuable bimetallic disc 15 located between the two base members. The stud 12 is adapted to be mounted in any suitable supporting means 16, shown more particularly in Fig. 1 of the drawin s as comprising a plate, co-operating nuts 1 being provided at each side of the member 16 to hold the stud 12 in proper operative position relatively to the supporting means. Each of the base members 13 and 14 comprises two metal discs 18 and 19 each of substantially the same external and internal diameters, the two discs or plates 18 and '19 being secured. together at their inner portions by tubular clampingmembers 21 and of drawings, in side elevation with of a device embodying 21a, respectively, havin the end portions thereof spun over, as is s own more particularly in Fig. 1 of the drawings. A sheet 22, of mica, is located against the outer face of the metal plate 19 and a plurality of arcuate contact terminal members 23 and 24, and contact terminal members 25 and 26 are mounted against the outer surface of the respective mica plates 22 on the individual base members 13 and 14. An inner disc 27 of mica is provided and located against the outer surface of the mica disc 22 to serve as a guide for holding the contact members 23 and 24 and the terminal members 25 and 26 in proper operative position against the mica plate 22 and to prevent any turning movement thereof on the plate 22.

The contact members 23 and 24 are secured against the mica sheet 22 by studs 28 having relatively large expanded heads 29 which are located in suitable openings 31 provided in the respectlve plates 18, an annular member 32, of mica, being located in the depressions 31 to insulate the head 29 from the plate 19 and to serve also as a means for centering the stud 28 in an openin 33 provided in the plate 19. A thin meta disc 34 is located on the outer end of the stud 28 which is then riveted over, in order to tightly clamp the contact member 23 against the mica sheet 22.

The terminal members 25 and 26 are mounted on, and insulated from, the plates 18 and 19 in the same manner as hereinabove described for the contact members 23 and 24, by studs 35 that extend outwardly from the surface of the plate 18 in order to provide means for connectin the terminal members 25 and 26 to con uctors (not shown) in a manner well known in the art. As the construction of the securing means is substantially the same as that shown in Fig. 6, no further detailed description thereofus believed necessary.

The thermally-actuable bimetallic disc 15 is located between the two base members 13 and 14 and is provided with a plurality of contact bridging members 36 and 37 insulatedly mounted thereon, in such manner as to project therefrom at each side thereof. The mounting means comprises, more particularly, mica discs 38 located at each side of the disc 15 near the periphery thereof. A clamping pin 39 extending therethrcu h is provided with enlarged portions at t e in Fig. 1 of the drawing.

base member 14 with a outer surfaces of the mica discs 38, the contact bridging members 36 and 37 being loosely mounted on the members 39 to permitof their adjusting themselves into close operative engagement with the adjacent spaced ends of the contact and contactterminal members. The contact bridging members 36 located on one side of the disc 15 are staggered relatively to the bridging members 37 located on the other side of the disc 15 in order to provide space for that part of the mounting means projecting through the disc. 1

The supporting base 13 is held in a predetermined position on the screw-threaded stud 12 by two cooperating nuts 41 and 42 which engage the tubular clamping member 21. The supporting base 14 is similarly held in proper operative position on another part of the stud 12, which part is of less diameter thanthe other part, by cooperating nuts 43 and 44 substantially as shown in Fig. 1 of the drawings. The disk 15 is held in its proper operative position by a nut 45 located in spaced relation relatively to a shoulder portion of the stud 12 as also shown The nut 45 should be so located that the disc 15 is loosely mounted between the shoulder and the nut 45. A pin 46 is mounted in the base member 14 and fits loosely in an opening in the disc 15, to prevent any turning movement of the loosely mounted disc on its support.

The bimetallic disc 15 is given an initial set or distortion, as is more particularly described and claimed in Patent N 0. 1,448,240 to J. A. Spencer, and as is there clearly described, will move from one operative position to another with a snap action. Because of its initial deformation, it will have a relatively large temperature difl'erential between its two operating positions, that is, the temperature variation necessary to cause the disc to move from the one to the other of the two limiting positions will be relatively large.

As an example of this operation, it may be mentioned that a particular thermostatic disc will operate at a maximum temperature of 600 degrees F.,but will not return to its initial osition until the temperature has dropped to 500 degrees F. If the initial position of the bimetallic disc 15 is as shown in Fig. 1 of the drawing, the base member 14 may be caused to move toward the bimetallic disc 15 a predetermined amount and this amount may be such as to cause the maxlmum temperature at which it will operate to be reduced from 600 F. to, say 550 F.

If the device is subjected then, to a temperature of 550 degrees F., or over, the bimetallic disc 15 is actuated away from the contact bridging members 36 are caused thereby to engage the terminal members on the base portion 13. If the base portion 13 and the contact members supported thereby are caused to move toward the right a predetermined amount, and then held by the nuts 41 and 42, the operating temperature of 500 degrees will be changed to, say 525 degrees, and the temperature need drop only to the latter'figure to cause the bimetallic disc to return with a snap action to its initial position substantially as shown in Fig. 1 of the drawing.

Hence, by varying the position of the base members 13 and 14, and by maintaining them in these predetermined positions, it is possible to reduce the relatively large ture diflerential initially characteristic of the snap-acting disc into a relatively small amount, whereby it is possible to maintain a much closer regulation of the temperature than would otherwise be the case.

It may be noted further that the particular construction shown in the drawings provides not less than six breaks or gaps for the'current normally traversing the circuit, and that therefore, it is possible to interrupt a relatively large value of current, particularly so as the disengagement of the contact bridging members from the contact members is effected at a relatively very high speed and therefore, in a very short space of time.

- The mounting of the contact bridging members directly upon the bimetallic disc permits of direct operation thereof by the quick-acting bimetallic disc, thus providing a very simple and eflicient switch structure for interrupting an electric circuit with a snap action and Without the interposition of additional springs and levers.

It may further be noted that all of the main elements of the device are mounted on a single supporting member and that adj ustment of the device is effected easily and quickly.

Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof, and I desire that only such limitations shall be placed thereon as are imposed by the prior art.

I claim. as my invention:

1. In a thermally-actuable switch, in combination, a supporting means, a bimetallic disc loosely mounted on said supporting means, contact bridging members ins latedly mounted on the disc, plates adjustably supported by the supporting means at both sides of the disc, and contact members on said plates alternately engaged by the bridging members.

2. In a thermally-actuable switch, in combination, a rod member, a pair of base plates, mounted on said rod in opposed spaced relasnap action and the tion, contact members on said base plates, :1

temperathermostatic member on said rod, located between said base plat-es and operable into its opposed limiting positions with a snap action at predetermined temperatures, and means for selectively varying the predetermined temperatures of operation.

3. A thermostatic switch comprising a support, a bimetallic disc mounted thereon, said disc being operable to reciprocally defiect from one normal position to another with a snap motion in response to temperature changes of predetermined values, and adjustable means for limiting the deflections of said disc to positions intermediate said normal positions whereby the temperature changes required to effect a reciprocal deflection of said disc may be adjusted to any desired value.

In testimony whereof, I have hereunto subscribed my-name this 14 day of April 20 HOWARD D. MATTHEWS. 

